Membrane bioreactor (MBR)

A MBR possesses all typical features of the conventional activated sludge process (anaerobic/anoxic/aerobic treatment of organic compounds and nitrogen) except for the settlement tank. The main difference is that the sludge is 100 % confined to the MBR due to the membrane filtration with a cut-off <0,4 µm – a conventional sedimentation basin becomes unnecessary. Generally spoken there are two different MBR systems, namely external cross flow and submerged systems. Looking at the submerged type the membrane is installed directly in the aerobic nitrification basin (see Sketch). 

An aeration device below the membranes provides an air-stream and thus a coupled hydraulic flow along the membrane surface. The cleaned water is filtrated through the fine pores of the membrane (= permeate) and flows through the hollow fibers to two permeate pipes. The hydraulic flow and extraction of the permeate is achieved through a suction pump or slight hydraulic pressure gradient and is therefore energetically highly efficient (appr. 0,12 kWh/m3). 



The main advantages of the MEMJET process are: 
  • Smaller treatment volumes – savings on land
  • No wash-out of biomass due to 100 % withdrawal of biomass on membrane surface
  • Enhanced biological degradation due to highly specific biomass and high sludge age
  • No influence of peak flows on quality of permeate (= clean water)
  • Germ free effluent